The invention relates to improvements in torque transmitting systems in general, and more particularly to improvements in so-called hydrodynamic or hydrokinetic torque converters.
A hydrokinetic torque converter which can be modified and improved to embody the present invention is disclosed, for example, in published German patent application No. 44 20 959 A1. A torque converter of the type disclosed in this published German patent application comprises a rotary housing which can be driven by the output element of a prime mover (such as a crankshaft or a camshaft of an internal combustion engine in the power train of a motor vehicle), a pump which is mounted in and is driven by the housing, a turbine which is rotatably mounted in the housing and can transmit torque to a coaxial output element of the torque converter, an optional stator which can be installed in the housing between the pump and the turbine, and a so-called lockup or bypass clutch which can be engaged to transmit torque from the housing directly to the output element.
Torque converters of the above outlined character are frequently combined with a hydraulic or hydromechanical torque sensing or monitoring device (hereinafter called torque sensor or sensor for short) which is normally designed to establish in a hydraulic supply conduit a fluid pressure proportional to the magnitude of transmitted torque. Such sensors are normally or often employed in conjunction with hydrokinetic torque converters which are designed to transmit torque from a prime mover to a continuously variable transmission (CVT). A torque sensor which is employed in conjunction with a hydrokinetic torque converter for controlled transmission of torque to a continuously variable transmission serves to ensure that one or more force transmitting parts are automatically acted upon with a pressure which is a function of the torque to be transmitted by the transmission.
A continuously variable transmission with two adjustable sheaves or pulleys and an endless flexible torque transmitting element (such as a chain or a belt) trained over the pulleys is disclosed, for example, in published German patent application No. 42 34 294 A1. A torque sensor is associated with at least one of the adjustable pulleys in order to ensure that the arcuate portion of the endless flexible element which is trained over the at least one pulley is clamped with a force which is proportional to the magnitude of the torque to be transmitted by the respective pulley. For example, the torque sensor can comprise preferably spherical rolling elements cooperating with surfaces arranged to transmit clamping and/or other forces related to the ratio of and to the torque to be transmitted by the torque converter.
As a rule, a torque sensor is installed next to the housing of a hydrokinetic torque converter, for example, between the torque converter and a continuously variable transmission. Reference may be had, for example, to pages 181-196 of the 1990 edition of German xe2x80x9cVDI-Berichtexe2x80x9d (meaning: Reports by the Association of German Engineers). A drawback of such mounting of a torque sensor is that, though it is or can be made readily accessible, it contributes significantly to the bulk of the power train, especially as considered in the axial direction of the torque converter.
Reference may also be had to commonly owned U.S. Pat. No. 5,667,448 granted Sep. 16, 1997 to Oswald Friedmann for xe2x80x9cPOWER TRAINxe2x80x9d. The patented power train employs a torque sensor which is installed between two torque transmitting systems in the form of clutches and an adjustable pulley of a continuously variable transmission. That clutch which is at least partially engaged receives torque from the output shaft of a prime mover, e.g., an internal combustion engine in the power train of a motor vehicle. In a motor vehicle wherein the space under the hood is at a premium, the placing of a torque sensor as a discrete part between neighboring constituents of the power train is likely to increase the overall axial length of the power train to an extent which renders the power train unsuitable for use in certain types of motor vehicles.
U.S. Pat. No. 4,577,737 (granted Mar. 25, 1986 to Niikura et al. for LOCK-UP TORQUE CONVERTER AND METHOD FOR CONTROLLING CLUTCH SLIP IN LOCK-UP TORQUE CONVERTER) discloses a hydrokinetic torque converter with a lockup clutch and an electromagnetic torque sensor which is surrounded by the pump as well as by the turbine of the torque converter and is installed radially outwardly of the radially inner portion of the piston of the lockup clutch. Such distribution of the pump, turbine, lockup clutch and torque sensor in the housing of the torque converter contributes significantly to the space requirements of the torque converter, particularly in the radial direction of the housing.
An object of the invention is to provide a novel power train which can be utilized, for example, in a motor vehicle and embodies an improved combination of a torque converter with a torque sensing or monitoring device (sensor or torque sensor).
Another object of the invention is to provide a simple, compact and reliable combination of a hydrokinetic torque converter and an automatic torque sensor.
A further object of the invention is to provide a hydrokinetic torque converter which embodies a torque sensor.
An additional object of the invention is to provide a novel and improved combination of a hydrokinetic torque converter, which embodies a torque sensor, with a prime mover, such as the internal combustion engine of a motor vehicle.
Still another object of the invention is to provide a hydrokinetic torque converter which embodies a torque sensor and is constructed and assembled in such a way that its space requirements (as considered in the axial direction of its constituents) need not exceed the space requirements of a standard torque converter which does not embody a torque sensor.
A further object of the invention is to provide a novel and improved method of increasing the combined mass of rotary parts of a torque converter which embodies a torque sensor.
Another object of the invention is to provide a novel and improved torque sensor which can be installed with advantage in the housing of a hydrokinetic torque converter but can be utilized also in many other (additional) ways and fields.
An additional object of the invention is to provide a torque sensor which constitutes an improvement over and a further development of devices disclosed in German patent application No. 195 44 644 A1.
Still another object of the invention is to provide a novel and improved twin-chamber torque sensor.
A further object of the invention is to provide a motor vehicle which embodies a hydrokinetic torque converter and a torque sensor of the above outlined character.
Another object of the invention is to provide a torque converter and a torque sensor which can employ a large number of simple and inexpensive parts.
An additional object of the invention is to provide a novel method of integrating a torque sensor into a hydrokinetic torque converter.
Still another object of the invention is to provide a novel and improved method of assembling the contents of the housing of a hydrokinetic torque converter in a manner which exhibits numerous important advantages as concerns the compactness, simplicity, useful life, initial and maintenance cost, and accessibility of the contents.
A further object of the invention is to provide a novel and improved housing for a hydrokinetic torque converter which embodies a so-called lockup or bypass clutch and a torque sensor of the above outlined character.
Another object of the invention is to provide a novel and improved lockup or bypass clutch for use in the above outlined hydrokinetic torque converter.
An additional object of the invention is to provide a novel and improved continuously variable transmission which cooperates with or embodies one or more hydrokinetic torque converters and torque sensors of the above outlined character.
Still another object of the invention is to provide a hydrokinetic torque converter which can be utilized, for example, in the power trains of motor vehicles as a superior substitute for presently known and utilized torque converters.
A further object of the invention is to provide the above outlined hydrokinetic torque converter with novel and improved signal generating means.
Another object of the invention is to provide a novel and improved mode of transmitting torque from the housing directly to the output element of a hydrokinetic torque converter.
The invention is embodied in a hydrokinetic torque converter which comprises a housing adapted to rotate about a predetermined axis and including a driving section arranged to receive torque from an output component of a suitable prime mover, e.g., from a camshaft or a crankshaft of an internal combustion engine in the power train of a motor vehicle. The housing accommodates a rotary pump, a rotary turbine and an optional stator, and the torque converter further comprises an engageable and disengageable lockup clutch or bypass clutch (hereinafter called lockup clutch) which is provided in the housing and spacedly surrounds the predetermined axis. Still further, the torque converter comprises a torque sensing or monitoring device (hereinafter called sensor or torque sensor) which, in accordance with a feature of the invention, is disposed in the housing between the turbine and the driving section, as seen in the direction of the predetermined axis, and radially inwardly of the lockup clutch.
The aforementioned output component of the prime mover can be said to constitute a rotary input member of the torque converter and is (directly or indirectly) non-rotatably connected with the driving section of the housing.
The torque converter further comprises a rotary output element preferably including a shaft which is arranged to drive a transmission (i.e., which can constitute a rotary input element of the transmission). The output element can further comprise a tubular hub which non-rotatably surrounds the shaft and is arranged to receive torque from the driving section of the housing by way of the turbine or directly by way of the lockup clutch. The transmission is or can constitute a continuously variable transmission (CVT).
The lockup clutch preferably comprises a piston which is mounted on the output element of the torque converter in such a way that it can move relative to the output element (e.g., relative to the aforementioned hub) in the direction of the predetermined axis but cannot rotate relative to the output element. A friction surface of the driving section of the housing is in (direct or indirect) frictional torque transmitting engagement with a friction surface of the piston in the engaged condition of the lockup clutch, and the driving section is rotatable relative to the piston in the disengaged condition of the clutch.
If the rotary output member of the prime mover is not directly connected to the driving section of the housing, the indirect connection between such parts can include a flexible plate-like torque transmitting member which is interposed between and is non-rotatably connected with the output member as well as with the driving section. As already mentioned above, the output member of the prime mover can constitute a camshaft or a crankshaft of an internal combustion engine.
The flexible torque transmitting member may but need not be directly connected with the driving section of the housing of the torque converter. In accordance with a presently preferred embodiment of the invention, the indirect connection between the flexible member and the driving section can include an annular plate-like connector and means for separably securing the connector to the flexible torque transmitting member.
The torque converter can further comprise an auxiliary mass which is affixed to the driving section of the housing and/or to the flexible torque transmitting member and/or to the annular plate-like connector and is located at that side of the driving section which faces away from the clutch, namely toward the output member of the prime mover. For example, the auxiliary mass can be affixed to the flexible torque transmitting member by bolts and nuts, screws and/or other types of threaded fasteners extending through openings provided for the fasteners in the flexible torque transmitting member and/or in the connector. The auxiliary mass can include or constitute a casting.
The connector and the flexible torque transmitting member can be designed and mounted to define an annular space for an auxiliary mass. The latter can be provided with an annulus of signal generating recesses, for example, in that (outer) side of the auxiliary mass which faces away from the axis of the rotary housing. Alternatively, the auxiliary mass can constitute an annulus having a circumferential surface provided with a groove (such as a circumferentially complete groove), and the signal generating means (e.g., for generating signals which can be processed to denote the RPM and/or certain angular positions of the auxiliary mass) then further comprises a shroud (e.g., in the form of a washer or ring) surrounding the circumferential surface of the annular auxiliary mass and provided with signal generating openings in the form of windows in register with the adjacent portions of the groove. The shroud can include or constitute a ring of metallic sheet material, and its windows can form an annular array in that they are spaced apart from each other in a circumferential direction of the aforementioned surface of the auxiliary mass.
The flexible torque transmitting member of the means for connecting the driven section of the housing to the output member of the prime mover can have a substantially circular outline, and the auxiliary mass can be provided with a tubular portion defining a recess for the radially outer marginal portion of the flexible member. In other words, a portion of the auxiliary mass can surround the flexible member.
Alternatively, the flexible torque transmitting member can have a polygonal outline (e.g., that of a triangle, particularly an equilateral triangle), i.e., the flexible member can be provided with several corners which are received in complementary recesses in that side of the auxiliary mass which faces away from the driving section of the housing.
A standard annular starter gear can be provided to surround and to be affixed (e.g., welded) to the periphery of the flexible torque transmitting member, of the connector or of the auxiliary mass. For example, the starter gear can be mounted on the aforementioned tubular portion of the mass, i.e., on that portion which surrounds the periphery of the flexible torque transmitting member.
In lieu of consisting of or including a casting (or in addition to a casting), the auxiliary mass can consist (at least in part) of a suitable metallic sheet material, e.g., a ductile material which can be readily shaped in a number of ways including several presently preferred procedures. For example, the auxiliary mass can include or constitute an annulus and includes a radially inner portion as well as a radially outer portion which is affixed to the driving section of the housing. The radially inner portion of such auxiliary mass can include two layers extending substantially radially of the predetermined axis and overlying each other (as seen in the direction of such axis). The radially outer portion of such auxiliary mass can be of one piece with one of the two overlying layers of the radially inner portion of the auxiliary mass. For example, the radially outer portion of the auxiliary mass and the one layer of the radially inner portion of such auxiliary mass can make an angle which is or at least approximates 90xc2x0.
Alternatively, an auxiliary mass which consists (at least in part) of a metallic sheet material can include a radially inner portion adjacent the flexible torque transmitting member, and a radially outer portion including two interfitted tubular layers adjacent the driving section of the housing. One of the two layers is of one piece with and is inclined (e.g., at an angle of at least substantially 90xc2x0) relative to the radially inner portion of such auxiliary mass. The one layer is surrounded by the other layer of the radially outer portion of the auxiliary mass. The connector can include a tubular radially outer portion which extends in the direction of the predetermined axis toward the driven section of the housing, and such tubular radially outer portion of the connector can include a first layer surrounding the layers of the radially outer portion of the flexible torque transmitting member as well as a second layer which surrounds the first layer of such radially outer portion of the connector.
Such torque converter can further include externally threaded male fasteners which are affixed to the connector and extend in substantial parallelism with the predetermined axis in a direction away from the driving section of the housing and through openings provided for such male fasteners in the flexible torque transmitting member and in a radially extending substantially washer-like portion of a ring-shaped attachment, preferably an attachment having a radially extending annular portion and an axially extending annular portion making with the radially extending annular portion an angle of at least close to 90xc2x0. The radially extending portion of the attachment can be said to constitute a washer which preferably overlies the flexible torque transmitting member. The axially extending annular portion of such attachment can be said to constitute a tube which at least partially surrounds the radially outer portion of the connector. Such torque converter preferably further comprises female fasteners (e.g., nuts) which mate with the male fasteners and are outwardly adjacent the washer-like radially inner portion of the attachment to thus secure the attachment to the connector. Rivets can be utilized to secure the washer-like radially inner portion of the attachment to the flexible torque transmitting member of the means for transmitting torque from the rotary output member of the prime mover to the driving section of the housing of the improved torque converter. The tubular radially outer portion of the attachment can be provided with an annulus of signal generating windows.
In accordance with a further presently preferred embodiment, the auxiliary mass can be of one piece with the driving section of the housing. For example, the auxiliary mass and the driving section of the housing can constitute a one-piece metallic casting. The flexible torque transmitting member can be secured to the auxiliary mass by male fastener means having externally threaded portions (such as the shanks of screws or bolts) extending into tapped bores of the casting including the auxiliary mass and the driving section of the housing.
The auxiliary mass which is of one piece with the driving section of the housing of the torque converter can be provided with a recess at that side which faces away from the turbine, and such recess can receive the radially outermost marginal portion of the flexible torque transmitting member. Such flexible member can have a polygonal outline with several corners, and the aforementioned recess of the auxiliary mass can include portions which snugly receive the corners of such polygonal flexible torque transmitting member. The polygonal outline of such flexible member can be that of an equilateral triangle.
The driving section of the housing, and particularly that driving section which is of one piece with the auxiliary mass, can be of one piece with a centrally located hub coaxial with the housing of the torque converter and (directly or indirectly) connectable with the rotary output member of the prime mover for the torque converter.
The housing of the torque converter further comprises a second section which is welded to or otherwise connected with and hence rotated by the driving section. The second section can be designed to rotate the pump and rotatably surrounds the aforementoned output element of the torque converter. The piston of the lockup clutch is rotatable with the turbine and can include a conical radially outer portion which engages a complementary second conical portion provided on (and preferably but not necessarily forming part of) the driving section of the housing when the lockup clutch is engaged. The conical portions of the piston and of the driving section confront each other, and the lockup clutch preferably further comprises at least one friction lining which is affixed to one of the conical portions and is engaged by the other conical portion in the engaged condition of the lockup clutch. The piston is movable in the direction of the predetermined axis toward and away from the driving section of the housing to respectively engage and disengage the lockup clutch, and the torque sensor can comprise neighboring profiled annular members in the form of discs having confronting ramps. Such torque sensor further comprises one or more spherical or otherwise configurated spreading elements between the two profiled members to move one of the profiled members axially and away from the other profiled member when one of the profiled members is caused to turn relative to the other profiled member. The first profiled member of the torque sensor is arranged to rotate with the output element of the torque converter, and the second profiled member is arranged to rotate with the piston about the predetermined axis and to move relative to, the piston in the direction of such axis.
The just described piston of the lockup clutch can comprise a radially inner portion including a tubular flange which extends in the direction of the predetermined axis toward the driving section of the housing. Such torque converter can further comprise a first annular member which is non-rotatably connected with the radially inner portion of the piston and has a tubular radially inner portion provided with internal teeth, a second annular member having external teeth mating with the internal teeth of the first annular member and a radially inner portion which is rotatable relative to the output element of the torque converter about the predetermined axis and is movable relative to the output element in the direction of the predetermined axis, and a third annular member including a radially outer first tubular portion rotatable relative to the tubular flange of the piston about the predetermined axis and movable relative to the flange of the piston in the direction of the predetermined axis. The third annular member further comprises a radially inner second tubular portion which is non-rotatably mounted on the second annular member, and the second profiled annular member of the torque sensor can include a radially outer portion provided with external teeth in mesh with internal teeth provided on a second tubular portion of the third annular member. Such torque converter can further comprise an annular plunger which is non-rotatably provided on a radially inner portion of the second profiled annular member of the torque sensor and includes a tubular first portion extending in the direction of the predetermined axis toward the second section of the housing, a second portion extending from the tubular first portion outwardly toward the lockup clutch, and a tubular third portion which extends from the second portion of the plunger toward the driving section of the housing and sealingly engages the tubular first portion of the third annular member. The third portion of the plunger is rotatable relative to the tubular first portion of the third annular member about the predetermined axis and is movable relative to the tubular first portion of the third annular member in the direction of the predetermined axis.
The second portion of the plunger can extend radially or at least substantially radially of the predetermined axis.
As mentioned above, the output element of the torque converter can comprise a hub and a shaft which is non-rotatably surrounded by the hub. The first profiled annular member of the torque sensor can be non-rotatably secured to the hub, the second profiled annular member of the torque sensor can be mounted on the hub for rotation about the predetermined axis in such a way that it can move relative to the hub in the direction of such axis, and the tubular first portion of the plunger can be mounted in sealing engagement with an annular external collar of the hub so that it is rotatable about the collar (i.e., about the predetermined axis) and is movable relative to the collar in the direction of such axis. The radially inner portion of the second annular member is rotatable on the hub about the predetermined axis and is movable relative to the hub in the direction of such axis. The plunger, the collar, the hub and the second and third annular members jointly define a fluid-containing plenum chamber, and the hub comprises at least one channel in communication with the plenum chamber for admission of a fluid (such as oil) into and for evacuation of fluid from the chamber.
The second profiled annular member of the torque sensor, the plunger, the collar of the hub and another portion of the hub preferably define a second fluid-containing plenum chamber, and the output element of the torque converter then defines at least one second channel which communicates with the second plenum chamber to permit admission of a fluid into the second chamber or to permit the fluid to flow from the second chamber in actual use of the torque sensor.
The third annular member can further include a portion which extends substantially radially of the predetermined axis and includes a tubular part sealingly engaging the hub. The tubular part is rotatable relative to the hub about the predetermined axis and is movable relative to the hub in the direction of such axis.
In accordance with a modification, the first profiled annular member of the torque sensor is non-rotatably secured to the hub of the output element of the torque converter, the second profiled annular member of the torque sensor is rotatable on the hub about the pre-determined axis and is movable relative to the hub in the direction of such axis, and the tubular first portion of the plunger is in sealing engagement with the annular external collar of the hub and is rotatable on the collar about the predetermined axis and movable relative to the collar in the direction of such axis. The radially inner portion of the second annular member is rotatable on the hub about the predetermined axis and is movable relative to the hub in the direction of such axis. The second profiled annular member of the torque sensor, the plunger, the collar of the hub and another portion of the hub jointly define a fluid-containing plenum chamber, and the output element of the torque converter defines at least one channel which communicates with the plenum chamber. The piston, at least one of the three annular members, the plunger and/or at least one section of the housing can be obtained by conversion of suitable sheet metal blanks in a deep drawing machine.
That (normally frustoconical) portion of the lockup clutch which is in frictional contact with the piston when the clutch is engaged need not always be of one piece with the driving section of the housing. Thus, such portion of the lockup clutch can constitute a discrete torque transmitting part which is non-rotatably affixed to the inner side of the driving section and is in frictional contact with the piston when the lockup clutch is at least partially engaged.
The driving section of the housing can include a wall which extends at least substantially radially of the predetermined axis, and the discrete torque transmitting part of the lockup clutch can be welded or otherwise affixed to such radial wall of the driving section. Alternatively, the discrete torque transmitting part can be affixed to a tubular wall forming part of the driving section and extending in the direction of the predetermined axis. For example, the discrete torque transmitting part can be laser welded to the radial or tubular wall of the driving section. Alternatively, such part can be riveted to the driving section.
The improved torque converter can further comprise means for centering the piston of the lockup clutch on the output element of the torque converter in the disengaged condition of the clutch. The centering means can comprise a substantially sleeve-like bearing member which is non-rotatably received in a central opening of the piston and surrounds the output element of the torque converter. An internal surface of the bearing member can be provided with a cylindrical portion and a conical portion, and the output element of such torque converter has an external surface including a cylindrical portion surrounded by the cylindrical portion of the internal surface of the bearing member and a conical portion which is complementary to the conical portion of the internal surface of the bearing member and abuts the conical portion of the internal surface in the disengaged condition of the lockup clutch.
The bearing member can be a press fit in the central opening of the piston of the lockup clutch, and a sealing device (such as an O-ring) can be interposed between the bearing member and the output element of the torque converter. For example, the bearing member can be provided with an internal groove for such sealing device. Alternatively, the sealing device can be installed in an external groove of the output element of the torque converter. The construction of the means for centering the piston in the disengaged condition of the lockup clutch can be simplified if the radially inner portion of the piston is provided with a conical internal surface complementary to a conical external surface which is provided on the output element of the torque converter and abuts the conical internal surface of the piston in the disengaged condition of the lockup clutch. The conical external surface of the output element can be provided with a circumferential groove for a sealing device which sealingly engages the conical internal surface of the radially inner portion of the piston in the disengaged condition of the lockup clutch.
The output element of the torque converter can be provided with a discrete centering member having the aforementioned complementary conical external surface, and at least a portion of such discrete centering member can consist of a suitable elastomeric material. Means can be provided to anchor the discrete centering member in the rotary hub of the output element of the torque conveter; such anchoring means can comprise an annular groove provided in the hub or in the discrete centering member and a projection provided on the discrete centering member or on the hub and received in the groove.
One of the complementary conical surfaces can be provided with an annular groove for an annular sealing device (such as an O-ring) which establishes a seal between the complementary conical surfaces in the disengaged condition of the lockup clutch.
An additional feature of the invention resides in the provision of novel and improved means for centering the driving section of the housing of the torque converter on the rotary output member of a prime mover. Such centering means can include the aforementioned flexible plate-like torque transmitting member which is connectable with the output member, and an annular plate-like torque transmitting connector serving to transmit torque between the flexible member and the driving section of the housing. The radially outer portions of the flexible member and the connector (namely those portions which are remote from the predetermined axis of the housing) can be non-rotatably affixed to each other by suitable securing means. Such securing means can include threaded fasteners in the form of screws, bolts and nuts or the like.
The connector can be provided with a hub which is coaxial with the housing of the torque converter and is received in a coaxial recess of the output member of the prime mover. Alternatively, the connector can include a centrally located centering section which surrounds a centrally located cylindrical external surface of the rotary output member of the prime mover. As already mentioned above, the output member of the prime mover can constitute a camshaft or a crankshaft of an internal combustion engine in the power train of a motor vehicle.
Still further, accurate centering of the driving section of the housing on the output member of the prime mover can be achieved by providing the driving section of the housing with a centrally located centering projection which is journalled in the rotary output element of the torque converter. Such centering projection may but need not be hollow and can extend in the direction of the predetermined axis toward the turbine in the internal compartment or space of the housing.
The connector can have a polygonal outline (such outline can at least approximate the outline of an equilateral triangle) and includes a plurality of corners which can be offset in the direction of the predetermined axis toward the flexible torque transmitting member of the means for centering the driving section of the housing on the output member of the prime mover. The flexible torque transmitting member is preferably provided with recesses for such corners of the polygonal connector. The connector can include portions which are bonded (e.g., welded) to the flexible torque transmitting member of the centering means.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved hydrokinetic torque converter itself, however, both as to its construction and the mode of assembling and operating the same, together with numerous additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.